Most Trichomycetes are parasites or commensals inside the guts of living arthropods.

Class Zygomycetes includes 7 orders, 30 families, 125 genera, and almost 900 species (about 1% of the known species of fungi). Its members include fast-growing, primary colonizers of substrates containing accessible carbon sources such as sugar and starch.

The best known representative of this phylum is black bread mold.